Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1981 Bionomics of Culex pipiens pipiens L., Culex restuans Theob., and Culex salinarius Coq. (Diptera: Culicidae) in central Iowa John Leslie Shipp Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Entomology Commons Recommended Citation Shipp, John Leslie, "Bionomics of Culex pipiens pipiens L., Culex restuans Theob., and Culex salinarius Coq. (Diptera: Culicidae) in central Iowa " (1981). Retrospective Theses and Dissertations. 6852. https://lib.dr.iastate.edu/rtd/6852 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. 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Signature was redacted for privacy. For the Major Department Signature was redacted for privacy. Iowa State University Ames, Iowa 1981 ii TABLE OF CONTENTS Page INTRODUCTION 1 REVIEW OF LITERATURE 4 Culex Mosquitoes 4 Culex pipiens pipiens L. 7 Culex restuans Theob. 16 Culex salinarius Coq. 22 Electrophoresis as a Means of Species Identification 28 MATERIALS AND METHODS 31 Description of Study Site 31 Description of Trapping Methods and Trapping Procedure 31 Species Identification 34 Parity in Culex Mosquitoes 35 Diapause in Culex Mosquitoes 38 Polyacrylamide-gel Disc Electrophoresis 39 RESULTS AND DISCUSSION 50 Seasonal Abundance of Culex Mosquitoes 50 Parity Studies in Culex Mosquitoes 68 Diapause in Culex Mosquitoes 75 Electrophoretic Identification of Culex Species 84 SUMMARY 97 LITERATURE CITED 101 iii Page ACKNOWLEDGMENTS APPENDIX; FORMULA 114 iv LIST OF TABLES Page Table 1. Anionic gel system 42 Table 2. Number of adult male Culex and egg rafts collected at Ames, Towa, 1978 and 1979 50 Table Al. Physiological saline for mosquitoes 114 V LIST OF FIGURES Page Figure 1. Electrophoretic gel tubes situated in the polymerization rack 44 Figure 2. Fluorescent light source 44 Figure 3. Upper and lower disc-electrophoresis chambers 48 Figure 4. Stained gel situated over the fluorescent light source 48 Figure 5. Seasonal abundance of Culex pipiens pipiens L. based on adult male collections at Ames, Iowa 53 Figure 6. Seasonal abundance of Culex pipiens pipiens L. based on egg raft collections at Ames, Iowa 55 Figure 7. Seasonal abundance of Culex restuans Theob. based on adult male collections at Ames, Iowa 58 Figure 8. Seasonal abundance of Culex restuans Theob. based on egg raft collections at Ames, Iowa 60 Figure 9. Seasonal abundance of Culex salinarius Coq. at Ames, Iowa, 197 9 63 Figure 10. Seasonal abundance of female Culex mosquitoes at Ames, Iowa, 1978 70 Figure 11. Seasonal abundance of female Culex mosquitoes at Ames, Iowa, 1979 72 Figure 12. Percentage of gravid Culex mosquitoes and fe­ male Culex with fat deposits of the over­ wintering type at Ames, Iowa, 1979 79 Figure 13. Seasonal abundance of gravid Culex mosquitoes at Ames, Iowa, 1978 82 Figure 14. Banding patterns of aldehyde dehydrogenase in nulliparous Culex mosquitoes 86 Figure 15. Isozyme patterns of aldehyde dehydrogenase in gels of nulliparous Culex pipiens pipiens L., Culex restuans Theob., and Culex salinarius Coq. 88 vi Page Figure 16. Banding patterns of aldehyde dehydrogenase in gravid Culex mosquitoes 88 Figure 17. Isozyme patterns of aldehyde dehydrogenase in gels of gravid Culex pipiens pipiens L., Ci^ex restuans Theob. , and Culex salinarius Coq. 9 2 1 INTRODUCTION Mosquitoes are vectors of several arboviruses such as Saint Louis encephalitis (SLE), western equine encephalomye­ litis (WEE), eastern equine encephalitis (EEE), and California encephalitis (CE) in North America. These encephalitides can significantly affect the health of humans and animals. Cases of arthropod-borne encephalitis have occurred in Iowa every year since 1967; the human cases usually involve LaCrosse (LAC) encephalitis which belongs to the CE group (W. A. Rowley, Department of Entomology, Iowa State University, unpublished data, 1980). An epidemic of SLE and WEE occurred in 1975, with 19 and 5 cases, respectively. The number of equine cases of WEE in Iowa yearly exceeds the number of human cases of all the arthropod-borne encephalitides (Dorsey et al., 1978). Two SLE and five WEE virus isolates have been obtained from Culex pipiens pipiens L., Culex pipiens quinquefasciatus Say, Culex restuans Theob., and Culex salinarius Coq. in Iowa from 1971-79 (Rowley et al., 1973; Dorsey et al., 1978; Wong et al., 1978; Rowley et al., 1979; W. A. Rowley, Department of Ento­ mology, Iowa State University, unpublished data, 1980). Adult females of these Culex species are morphologically similar and are difficult, if not impossible, to identify to species. This is especially the case if scales are missing as is the case in light trap specimens. However, adult males 2 and 4^^-stage larvae can be accurately identified. Recently, electrophoresis was employed to identify adult females of Cx. £. pipiens, Cx. p. quinquefasciatus, Cx. restuans, Cx. salinarius, and Culex territans Walk. (Saul et al., 1977). The importance of the Culex species (Cx. p. pipiens, Cx. restuans, and Cx. salinarius) to the natural history of SLE and WEE viruses is unknown in Iowa. The sympatric association of these species makes it difficult to attribute a virus isolation to one particular species. Culex p. pipiens is a primary vector of SLE in North America (Luby et al., 1969). However, it is questionable if Cx. p. pipiens transmits arbo­ viruses to humans, since these mosquitoes primarily feed on birds (Murphey et al., 1967; Ekis and Hagmann, 1968; Tempelis, 1975). It is possible that Cx. restuans and Cx. salinarius func­ tion in the natural history of SLE and WEE viruses. Both mosquito species transmit SLE virus, and become infected with WEE virus (Chamberlain et al., 1959; Hayes, 1979). Culex restuans feeds on birds (Murphey et al., 1967; Wright and DeFoliart, 1970). Culex salinarius feeds on humans (LeDuc et al., 1972; Edman, 1974). Important criteria for determining the vector status of mosquito species are: seasonal abundance; parity of females, and the time period of diapause induction. Some of these factors have been investigated for Cx. p. pipiens 3 but most have not been studied for Cx.